The present invention pertains to a progressive punch. In particular, the present invention pertains to a progressive punch for use in a strapping machine.
Strapping machines or strappers are well known in the art. These machines are used for strapping articles, e.g., a load, together with strapping material. Strapping material is offered in a variety of sizes and materials and is generally stored on a roll. Conventional strapping materials include steel and plastic.
Typically, a free end of strapping material is passed around the load until there is an overlap between the free end and the strapping material still connected to the roll. The overlapping portion of strapping material is placed between jaws of a strapping machine and the free end of the strapping material is fixed in place by a gripper portion of the machine. After the strapping material is fixed, the material is tightened or tensioned around the load to a desired tension. This is accomplished by operating a feed wheel to pull back or tension the strapping material.
A typical strapper includes sealing heads for sealing the free end of the strapping material onto itself, around the load. Typically, in manual (i.e., hand-operated) strappers, a handle is rotated which applies a force to cause a punch or sealing head to press down against the strap to seal the strap to itself. After the strapping material is sealed, the strapping material still connected to the roll is cut by a cutter, which is a portion of the strapper. This completes one strapping operation. This type of seal, which is effected by sealing the strap to itself, differs form those strappers that position a separate piece of material around the tensioned strap.
Considerable force is required to form the seal in the strapping material and to cut the material. As such, an operator may fatigue from repeatedly applying force while forming seals.
One known type of strapper uses a cammed arrangement by which the sealing heads are sequentially moved into engagement with the strap. Although this reduces the amount of force necessary to effect a seal, the mechanical movement (and thus the components required), is complex and results in increased maintenance to the strapper. In that many such strappers are used xe2x80x9cin the fieldxe2x80x9d increased maintenance typically results in a tool that has limited usefulness.
Accordingly, there is a need for a sealing head or punch that allows a sufficiently strong seal to be formed without requiring a sizeable actuating force. Desirably, such a sealing head includes one or more punch heads that are fixed relative to one another to provide this reduced-force arrangement. Most desirably, such a reduced-force arrangement is provided with a minimum of moving parts.
A progressive punch is used in a strapping machine that is used for positioning an associated strap material around an associated load and for readily forming a seal of the strap overlapped onto itself. An exemplary strapping machine includes a strapping machine body having a jaw assembly that includes first and second punch supports. The punch supports are configured to receive the strap therebetween. The first punch support includes two punches for engaging the strap; the second punch support includes one punch. Each of the punches includes at least two punching heads. The punches and punching heads are configured to cooperate with one another so that the punching heads progressively engage the strap, so that the first punching head initially engages the strap at a different time than the second punching head initially engages the strap.
The punching heads can include a base and a cutting edge so that they are attached to their respective supports at their respective bases.
The second punch support is fixed and the first support is movable toward and away from the second support so that the two punches on the first support engage the associated strap when an actuating force-is applied to the strapping machine such as by rotating an actuating handle.
The punches of the movable support engage a first surface of the associated strap at first and second positions, and the punch of the fixed support engages a second surface of the associated strap at a third position when the punches engage the associated strap. The third position is opposite to the first and second positions.
Other features and advantages of the present invention will be apparent from the following detailed description, the accompanying drawings, and the appended claims.